DISCLAIMER: Following these instructions and/or installing Front Row on a Mac that isn't officially supported by Apple for such purposes is done entirely at your own risk. I accept no responsibility for damage to any other software installed on your computer, damage to the computer itself, or damage to the brickwork of your house. Seriously: this worked on my iMac G4 running Mac OS X 10.4.7, but I give no guarantees that it'll work on whatever set-up you have. If you're have any doubts then don't do it!.

Download the disk image (which can be downloaded from the Front Row update page), open it, drag the file named FrontRowUpdate1.3.pkg onto your desktop (or other preferred location) and then, once the file has copied, eject the disk image. Control-click FrontRowUpdate1.3.pkg and select Show Package Contents from the pop-up menu. Navigate into the Contents folder and open the file FrontRowUpdate1.3.dist using TextEdit. To do this, simply Control-click on the file and select Open With > Other... from the pop-up menu, and then navigate to and select TextEdit from the resulting file dialog.

When the file is open, scroll down to around line 39 which should read something like:

Unfortunately, this only updates if you already have Front Row existing on your Mac, which my PowerBook G4 doesn't have. And I can't find where to get an earlier version to install so I can then update ;>}

I have tried several methods like this in the past. And although they have worked, it is still easier to download Front Row Enabler from Andrew Escobar's website. Front Row Enabler has been updated for Front Row 1.3 compatibility and has worked for me on several older systems including one that is running Tiger Server.

Tremendous! Thanks a lot.
I had to tweak a little more to get things running, though:
1. the correct link to front row is here
2. At first, I couldn't install it to my hard drive in spite of this hint, because front row was not yet installed (and this download from apple is labelled as an update). The solution was analogue to what is described above: in the same file, a couple of lines beneath, there is the following code:

At least, they made it obvious ;)
I deleted this (including the bracket), and - that was it!
Another way to arbitrarily lock us down, of course.
Also, from what I read, Front Row does not start unless you make Tiger believe you have an IR receiver. Just follow this hint. Oh, and finally, I had to go to my system preferences, mouse&keyboard pane, to set the keyboard shortcut for front row (it was greyed out).